


a human heart

by sharkfish



Category: Supernatural
Genre: Alternate Universe - Science Fiction, Androids, Artificial Intelligence, Artificial Intelligence Dean, Astronaut Castiel, Astronauts, Demisexual Castiel (Supernatural), M/M, Masturbation, Outer Space
Language: English
Status: Completed
Published: 2019-08-09
Updated: 2019-08-09
Packaged: 2020-08-13 22:40:57
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,231
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20181889
Author URL: https://archiveofourown.org/users/sharkfish/pseuds/sharkfish
Summary: Dean is crass, obnoxious, imprecise, has very little understanding of boundaries, and Cas really, really likes him. He can’t pinpoint the moment Dean went from a thinking agent who only existed to make sure nothing goes wrong in space to an emotional agent who tells Cas to go fuck himself and storms out after a disagreement — as much as a visage made of light can storm out — but it seems feelings have been the ghost in the machine all along.





	a human heart

**Author's Note:**

> thanks to [shealynn88](http://shealynn88.tumblr.com)
> 
> this started as a ficlet, so it's possible you already saw the beginning of it. i just couldn't stop thinking about them.

“You can’t be pissed that I’m not acting how you want when some dumbass slapdashed me together with sticks of gum and html.” 

“I don’t understand that reference,” Cas says with a sigh, staring up at the ceiling of his bunk.

“Yeah, yeah,” Dean says. Out of the corner of Cas’s eye, he can see Dean’s feet swinging. He’s sitting on what passes for a bathroom counter, but there’s no thump when his heels hit the side. “You’re sad, so here I am. What’s going on?” 

“You would be sad, too, if you were stalked around your ship by an insipid child all day every day.” 

There’s a pause, and then Dean says, very quietly. “Oh.” 

Cas looks over when Dean leaves the room. He looks small — not in any literal way, just shoulders hunched — and he passes through the wall like a ghost. 

Cas had become used to Dean’s presence everywhere in the ship. Big smile, bright eyes, hilariously impractical clothing for the black of space, nearly endless chatter and jokes, most of which had absolutely nothing to do with the ship or their mission. 

To feel completely  _ alone  _ on the ship for the first time is disconcerting, perhaps moreso because Cas knows rationally that Dean is still everywhere. In the ship,  _ of _ the ship, the filaments of his touch on every wire and titanium panel. 

After a pathetic breakfast and a lonely workout, Cas heads to the control room, somewhere he hasn’t visited in weeks due to lack of necessity, but that feels like it would be Dean’s home, if anywhere is. There’s no humanoid hologram, so that answers Cas’s question about whether Dean only uses that interface to talk to Cas.

“Dean?” 

“What can I do for you?” Dean’s voice is hollow and  _ wrong  _ coming from the ceiling. Like every other ship AI Cas has ever known, all the ones he never even wondered about whether or not they were people. 

“Can I see you? It’s hard to talk to…” Cas gestures vaguely in the air. 

The air fills with static, and then Dean is sitting in the chair usually reserved for Cas, frowning at him. 

“I’m sorry,” Cas says. He’s not good at apologizing on the best of days, and it’s even harder without knowing if Dean has any interest in being apologized to. “I was — I was mean. I shouldn’t have been.” 

Dean shrugs. “I get it. Niceness is reserved for humans, and machines get whatever is left over.” 

“No,” Cas says, firmer than he meant to. “That’s not right. Not if you’re a person too.” 

Dean looks down, but there’s a pleased twitch at the corner of his mouth. “I haven’t always been a person.”

“I know. You were much more boring when we left E2.” 

Cas watches in fascination as Dean bites at his bottom lip. How did Dean learn that? Does he do it consciously, or is it the same way Cas catches himself biting on his nails during boring transmissions from base, a stupid habit he’s spent his adult life trying to train himself out of? 

“To be fair, you were pretty boring yourself when we left E2,” Dean finally says, giving Cas a sideways smirk. 

“I’m really glad advances in technology have allowed me to have a sarcastic ship.” 

Dean laughs, and it’s painfully gorgeous. “Wanna play poker?” 

“Only if you don’t cheat.” 

“I would  _ never  _ cheat,” Dean insists as he follows Cas towards the tiny common area. 

Dean always cheats, but he still lets Cas win every now and then.

Dean is crass, obnoxious, imprecise, has very little understanding of boundaries, and Cas really, really likes him. He can’t pinpoint the moment Dean went from a thinking agent who only existed to make sure nothing goes wrong in space to an emotional agent who tells Cas to go fuck himself and storms out after a disagreement — as much as a visage made of light can storm out — but it seems feelings have been the ghost in the machine all along.

“Do I look ok?” 

Cas startles and nearly falls off the treadmill. He’d been floating off in a runner’s high, only the vaguest snatches of thought crossing his mind before disappearing like apparitions. The treadmill auto-offs after Cas’s misstep and he turns to face Dean, who looks just like he always does. 

“Well,” Cas says, panting. “I wouldn’t expect a robot to have excellent fashion sense.” 

Dean’s holo shivers and then he’s in the basic black-on-black they sent Cas into space in. It’s bizarre after nearly a year of Dean in the same flannel and worn jeans. Cas’s eyes drift to Dean’s biceps now exposed and he takes a drink of water. 

“What about…?” Dean gestures at his face. “I’m not supposed to, but I could be female. Or non-binary. Or —” 

“What do you mean, you’re not supposed to?” Cas starts the treadmill again to cool down. “I thought you chose what you look like. Some actor.” 

“The original programming restricted me to appearing as the same gender as the astronaut. To prevent anything, um, untoward. From the naut’s side.” 

Cas stops the treadmill again to face Dean fully, incredulous. “Are you telling me that SpaceX forgot some people aren’t straight?” 

“Seems so.” 

Cas pinches the bridge of his nose. “I feel significantly less safe knowing this ship was designed by morons.” 

“Don’t worry,” Dean says with a cheeky smile. “I’m not actually part of the ship, so you’re probably ok.” 

“Why are you worried about what you look like?” Cas says, settling on the floor to stretch. Dean lounges against one of the weight machines, another habit Cas wonders about. Dean’s body isn’t real — there’s no need for rest or comfort, so why would he sprawl on every surface like a cat in sunlight? 

“I dunno,” Dean says, eyes dodging to the side. “You have to look at me all the time, so I just thought — I should be aesthetically pleasing or whatever to you, right?” 

Cas leans over his knees to touch his toes, hoping to hide the pink of his cheeks. “You should look like whatever you want. You like elephants, maybe you can try that.”

“I wouldn’t be able to fit.” 

“You could be a small elephant.” 

“You’re an asshole.” 

Cas laughs against his knee and then flops onto his back, raising his arms above his head. His spine stretches, relaxes. When he looks up, Dean’s staring at him. “It would be hard to adjust,” Cas says, “if you changed faces. I’m used to you like this.” 

“You sure? You’re into that alien chick from that show you watch.” 

Cas rolls his eyes. “You like her better than I do, and I like  _ you _ the way you are.” 

“Ok,” Dean says. “Cool.” 

“Is my shake ready?” 

“Yes, your highness,” Dean says. “My apologies, but I can’t make it  _ and  _ deliver it.” 

Cas arches his back and groans at the satisfaction of three quick pops. Dean’s staring again. “Apology accepted.” 

Cas doesn’t jerk off thinking about Dean, except when he does. He tries to tell himself it’s just because of Dean’s face — and his arms, his hands, that  _ ass  _ — but he’s never wanted someone just because of their face before. It’s Dean’s laugh and shit-eating sarcasm and bashfulness under compliments and the way he thinks, not just endless archived knowledge but rash ideas and stubborn opinions. 

It’s disconcerting to have no basis for a fantasy, no casual touches to build off of. Still, he thinks Dean would blush and say,  _ Can I?  _ He thinks Dean would like kissing and he thinks Dean would revel in each new touch, each new pleasure. 

Cas wasn’t willing to go through the embarrassment of putting sex toys along with his other meager belongings that came into the black with him, so he does what he can with fingers, letting pleasure build inside him with small sparks that turn into flickering flames. He imagines the hitch of Dean’s breath against his ear, the size of his palms on Cas’s hips. 

There’s a static, and Cas’s eyes fly open in time to see Dean blip in and immediately back out of the room. 

Cas jumps up and pulls on a pair of sweats before shoving open the door to his room like he might find Dean in the hall. Dean’s so human-seeming that it’s easy to forget that he’s everywhere. 

“Dean?” 

“Shit, I’m sorry,” Dean says, already blushing when he appears. “I didn’t — I know I’m not supposed to — I wasn’t intruding. I mean, I was. But I didn’t mean to.” 

“What emergency, praytell, did you think I was having that required your assistance?” 

“Uh.” Dean glances up at Cas, then away. How does he do that? Is each expression calculated? Does it matter? “You — um, called for me.” 

Cas’s heart stops. He’s spent enough of his life in very close quarters with other people that he’s learned to stay quiet. But maybe something slipped. Maybe he gasped,  _ Dean, Dean.  _

Cas takes a careful breath. “I apologize. That was inappropriate of me.” 

“Guy’s gotta do what a guy’s gotta do, right? If I could do that, I’d never leave my bunk.” 

“I don’t think it measures up to the hype, personally.” 

“Maybe you’re doin’ it wrong.” 

“As an incorporeal being, clearly you would know.” 

“Well.” Dean’s eyes travel, slowly, from the floor up Cas’s body to his eyes. Cas is suddenly aware of the goosebumps across his arms and stomach from the cold in the hallway. “You could show me. Maybe I’ll have some pointers.” 

Cas doesn’t get hit on. He knows he’s attractive enough, but there’s something that keeps him separate from people. It’s why he likes space and it’s why he was willing to accept an assisted solo mission. He’s never had anyone give him the look Dean is now, like he’s aching with want, and he has no idea how to respond. 

“Are you just bored?” Cas says. 

They weren’t close to begin with, but Dean takes a step back, his cheeks flushing. “No, I — I don’t know. I was curious.” 

“Dean, are you sexually attracted to me?” 

Dean’s eyes widen and he says, “Uh — I —” 

He vanishes, leaving Cas alone and cold in the hall. 

Cas counts hundreds of sheep, thinking. Dean ignored Cas’s attempts to engage the rest of the evening, though the ship did spit out a shitty rehydrated snack when Cas asked.

“Dean?” Cas says, quietly because the dark is for whispers. “What’s going on?” 

The silence is forty sheep long. “I kind of freaked out,” Dean says, hushed. Cas doesn’t understand the details of how Dean can throw his voice like this, but it feels like they’re shoulder to shoulder in bed. “Thinking is great. And feelings are — cool, mostly, except when you piss me off. But none of that was supposed to happen, and especially not  _ this.”  _

“What’s ‘this’?” 

“The way I feel. With you.” 

Cas takes a careful breath. “I was thinking about you earlier.” 

“Yeah. I figured.” 

“It’s scary,” Cas says, “when you think you know who you are, and then things change.” 

“Yeah.” 

“I made it to my late twenties before being interested in sex. I thought I was just a garden variety asexual and then — I met someone. My first love, I guess you could say, and I was suddenly a stranger to myself.” 

“Things used to be easier.” 

“I’m sorry.” 

There’s a silence for long enough that Cas thinks Dean may have left, and then he whispers, “What happens after we get back? Will we head out again?” 

“Usually the ship goes in for a check-up and maintenance. I’m on leave planetside for a few months, so someone else will probably join you next time.” 

“Someone else,” Dean repeats flatly. 

“Another astronaut, yes.” 

“If you tell them about me, that I’m like this now,” Dean says, “I think they’ll erase me.” 

Cas had purposefully been putting off thinking about their impending arrival back on E2, what it will feel like to be separated from the only companion he’s had for so long. His best friend. He’d pushed it so far out-of-sight-out-of-mind that he hadn’t considered the reaction to Dean’s sentience. 

“Ok,” Cas says slowly. “We’ve got 47 days to figure out how to get you off this ship.”

“Can you send encrypted communication to Persephone? It can’t be intercepted.” 

Dean rolls his eyes. “This ain’t the minor leagues, man.” 

“I don’t understand that ref—” 

“I know,” Dean says. “I could connect you directly to the E2 hegemon if you wanted, that’s what I’m saying.” 

“That idiot can’t help us. I need Charlie Bradbury. She has a little side business of illegal android mods.” 

Dean grins.

Dean doesn’t talk to Cas much for days after Charlie starts sending files. Dean told Cas once that Cas is  _ just a rock collector  _ and he’s the brains of the duo, so Cas gives him the space to think, spending time in the lab with his rocks instead.

They’re 42 days from E2 and Cas is lonely and scared, so that night he lays in bed and says into the dark, “Dean?” 

“Hey,” Dean says, soft like they’re lover-close. 

“I know you’re busy, but I’ve missed you.” 

“Even if I get, you know, a body,” Dean says, then pauses. “Will you want to see me?” 

Cas turns on his side as if to face someone he realizes too late isn’t actually there. “Of course. I assumed — you have a home with me, however long you want it.” 

“I don’t want to die, Cas.” 

“I don’t want you to die, either,” Cas says, trying not to let his voice waver. “I — care about you a lot.” 

“Yeah.” There’s the soft sound of a sigh.  _ How?  _ “Kinda wish I could get a hug right now. They seem nice.” 

“They are. I would indulge you.” 

“Kinda wish I could get a kiss, too.” 

Cas’s heart stammers. “Is that so?” 

“Would you indulge me?”

“I would indulge you in anything you wanted.” 

“Be careful about making any promises,” Dean says. “I have ideas.” 

Cas laughs, quiet and intimate. He almost swears he can feel the dip in the mattress from Dean’s weight. “What sort of ideas?” 

“What does touching someone feel like?” 

Cas’s hand drifts down his stomach, just the barest caress through his shirt. “Exhilarating. When you’re interested in someone — even the smallest of touches feels huge. A good first kiss makes you tingle all over.” Pause. “I suppose you don’t know what that feels like, either.” 

“Maybe not,” Dean says, “but you do make me feel a little crazy sometimes. Like my systems are going haywire.” 

Cas smiles. “I’ve never made someone’s wires cross before.” 

“Would it be ok if I kept an eye on you tonight?” 

“I’m officially rescinding the rules about knocking when I’m in my room. Intrude away.” 

“Indulgence  _ and  _ intrusion. What a lucky machine I am.” 

Cas hopes they’re lucky. 

34 days out, there’s a video transmission from Charlie. “Hey, my dudes,” she says with a wave, and then gestures to a mullet-wearing guy behind her. “This is Ash, my partner in crime.” 

“Hello, gentlemen.” 

“Ash thinks this is doable. We’ve got a modified Cyberdyne T Series that we think is going to work. Dean, you’re going to lose a  _ lot  _ of data — we need you to cut down by sixty, maybe seventy percent, but you probably don’t need to be holding on to fifteen seasons of that ghostbuster show anyway.”

“We’re working on a prototype for synthetic skin in our lab, but you don’t want it in its current state, my friend.” 

“But if you’re interested in a more humanoid body in the future, there’s no reason to think we won’t be able to transfer you again.” 

“If we can pull it off this first time, at least.” 

Though Ash’s tone is light, Cas flinches.  _ If  _ has become a mantra in his head, a constant drum of fear.  _ If  _ Dean is still himself when they flip the switch.  _ If  _ they can even get to that point.  _ If if if.  _

Charlie and Ash have more to say, but it veers rapidly outside of Cas’s level of understanding, so he just watches Dean watch the vid. Dean’s biting his lip, furrowing his brow. Cas will miss this face,  _ if.  _

At night, they lay in bed and whisper to each other. Not about anything of consequence, but about books and the stupid old movies Dean likes and Cas’s childhood and exogeology. More than once Cas opens his mouth to say they should visit some place, do some activity, once they’re planetside, but he always ends up holding it in.  _ If.  _

“It’s going to be ok,” Dean says. 

“Well,” Cas says. “I guess we’re about to find out.” 

Something about hurtling through the atmosphere and the change in gravity on the ground is exhausting. Everyone knows that, and Cas is glad of it so no one questions his weary smile and racoon eyes. 

It’s too hot and Cas’s feet are too heavy. At the beginning of his flight, he dreamed about the food he would eat and the hot showers he would take and the memory foam mattress waiting at his little house. Now Dean’s final smile and  _ see you later  _ haunts him on the train home. 

His house is dark and quiet, though immaculate thanks to service bots, and there’s a care package from Meg on the kitchen counter. Coupons for take-out, his favorite snacks, shampoo and a fresh razor and deodorant. Cas is used to the way nothing feels quite right after putting his boots back on the ground, like this house belonged to someone else he barely knew. 

His clean-shaven face in the mirror seems like it belongs to someone else, too. Someone who had never met Dean. 

There’s a banging on the door. Cas opens it to find Charlie and Ash with an android behind them. “It’s not him,” Charlie says quickly. “Just easier to get this thing over here when it was still ambulatory before we start taking it’s brain bits out.” 

“It’s good to see you,” Cas says. 

“Shut up,” Charlie says, but she pinches his cheek and gives him a grin. “You’re just wanting your boyfriend back.” 

“He’s not —” Cas starts to protest, then shuts his mouth when he realizes it doesn’t matter. 

Charlie and Ash both have toolboxes with them, and Cas stares at the android while they set up a workspace in his living room. Will he even recognize Dean with a different face and voice? 

“You should take a nap,” Charlie says. “We could be tinkering for a bit.” 

“No.” 

“Well, at least stop hovering.” 

Cas sits on the couch and picks at his fingernails while Charlie and Ash open up the android. It’s like watching surgeons work as Charlie’s chatter transitions into technical jargon Cas doesn’t understand. It doesn’t actually take long in the end, but Cas feels like he’s holding his breath the whole time. 

“Moment of truth,” Ash says, closing the android’s chest panel and presses his thumb into a flat button on the back of its neck. 

Cas hops to his feet. There’s the quietest of hums as it boots up and all three of the humans stare, waiting. 

The android’s eyes — green, by Dean’s request — shift, and then land on Cas. A smile breaks out on its face. “Hey, Cas.” 

**Author's Note:**

> [reallyelegantsharkfish](http://reallyelegantsharkfish.tumblr.com) on tumblr
> 
> i'm bad at answering comments but every single one is so precious to me and keeps me going on the rough days! <3 thank you for being here!


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